1. Field of the Invention
This invention relates to optical switching devices and more particularly, to devices which achieve switching by mechanically coupling different ones of light-transmitting optical fibers.
2. Description of the Prior Art
Disclosed in an article entitled "Mechanical Optical-Fibre Switch" by P. G. Hale and R. Kompfner, in Electronics Letters, Volume 12, No. 15, July 22, 1976, is an optical switch which utilizes a loose-fitting sleeve having an interior square cross section for accommodating the ends of the light-transmitting optical fibers to be coupled. A first fiber enters the sleeve from a first sleeve end and a pair of second fibers enter the sleeve from a second sleeve end. The ends of the second fibers bias against opposite corners of the cross section with the ends in one plane. The end of the first fiber is positioned near the ends of the second fibers. Switching is achieved by aligning the first fiber in the corner of the selected second fiber.
Two techniques for moving the first fiber are disclosed in the Hale et al article. The first technique is by pushing the first fiber transversely outside the sleeve. In the second technique disclosed, the first fiber is coated with a ferromagnetic sleeve near its end and rigidly secured to the sleeve at a point remote from its end. Movement of the first fiber is achieved by applying magnetic forces to the ferromagnetic sleeve with an electromagnet.
There is need to develop an improved optical switching device. In the first technique in Hale et al, it is difficult to seal the first sleeve end of the sleeve to prevent contamination of the fiber ends because the first fiber is moved from outside the sleeve. In the second Hale et al technique using an electromagnet, biasing the first fiber against either corner requires a continuous supply of energy, as well as a precisely controlled magnetic force.
Also, such a device should be reliable and durable for extended use. A light-transmitting optical fiber is very fragile and yet the first Hale et al technique requires its direct manipulation for switching. In the second Hale et al technique, breakage of the sleeve or of the first fiber can occur during magnetic force generated movement of the first fiber against the sleeve or the sleeve against the electromagnet.
Desirably, a mechanical optical fiber switching device can be developed which is easy to manufacture, compact, reliable, protective of the fibers against contamination, and inexpensive.